Wafer-Level Camera Lens Bonding with FFL Compensation Films
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Solution Overview
Problem
Existing wafer-level bonding processes for camera lenses struggle with FFL variations, leading to performance issues and failure to meet tight design tolerances, especially in high-end camera lenses, requiring costly and time-consuming individual lens focusing and bonding processes.
Innovation Solution
A wafer-level bonding method that involves measuring and analyzing the FFL of each lens, forming thin transparent films on the sensor wafer based on compensation values, and aligning and bonding the lens wafer with these films to adjust the focal length, using a Step-and-Repeat molding method with optical polymers to minimize refractive index differences and achieve precise thickness control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wafer-level bonding process is used to fabricate camera lenses, then productivity is improved, but FFL variations cause lenses to fail performance specifications
Solution Approach 1:
The patent measures and records the FFL of each lens before wafer-level bonding, then uses this pre-measured data to determine the thickness of compensation films to be formed on corresponding sensors. This preliminary measurement and planning enables subsequent wafer-level bonding to proceed without individual lens handling, maintaining both high productivity and precise FFL compensation.
Solution Approach 2:
The patent forms thin transparent films with different thicknesses on different sensors based on the specific FFL compensation needs of each corresponding lens. This localized customization of film thickness allows each lens-sensor pair to achieve optimal focus while maintaining wafer-level bonding efficiency.
2Manufacturing precision
If die-level pick and place process is used to bond individual lenses to sensors, then FFL accuracy is improved, but fabrication cost increases
Solution Approach 1:
The patent measures and records the FFL of each lens before wafer-level bonding, then uses this pre-measured data to determine the thickness of compensation films to be formed on corresponding sensors. This preliminary measurement and planning enables subsequent wafer-level bonding to proceed without individual lens handling, maintaining both high productivity and precise FFL compensation.
Solution Approach 2:
The patent introduces thin transparent films as intermediary elements between lenses and sensors. These films serve as compensation mechanisms that adjust the optical path length to compensate for FFL variations, enabling wafer-level bonding to achieve the precision previously only attainable through individual lens focusing.
3Manufacturing precision
If active focus method is used to find best focus, then image quality is improved, but fabrication cost increases
Solution Approach 1:
The patent measures and records the FFL of each lens before wafer-level bonding, then uses this pre-measured data to determine the thickness of compensation films to be formed on corresponding sensors. This preliminary measurement and planning enables subsequent wafer-level bonding to proceed without individual lens handling, maintaining both high productivity and precise FFL compensation.
Solution Approach 2:
The patent replaces the active focus method (which requires image capture and feedback analysis) with a passive optical compensation approach using thin transparent films. This substitution eliminates the need for expensive active focusing equipment and processing while achieving equivalent or superior focus accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces FFL variations, improves productivity, lowers fabrication costs by eliminating individual lens handling, and enhances the ability to meet tighter design tolerances, while maintaining high image quality and reducing the need for active focusing.
Implementation Method 1
forming thin transparent films on the sensor wafer based on compensation values... using a Step-and-Repeat molding method with optical polymers to minimize refractive index differences
Data Source
AI summary
A wafer-level bonding method for fabricating wafer level camera lenses is disclosed. The method includes: providing a lens wafer including lenses arranged in an array and a sensor wafer including sensors arranged in an array; measuring and analyzing an FFL of each lens to obtain a corresponding FFL compensation value for each lens; forming a thin transparent film (TTF) on each sensor of the sensor wafer, and the thickness of TTF is determined by the FFL compensation value of the corresponding lens; aligning and bonding the lens wafer with the sensor wafer having TTFs formed thereon. Since the focal length of each lens is adjusted to compensate the FFL of the lens by adding a TTF of transparent optical material with an index of refraction that is similar to the index of refraction of the sensor cover glass, the FFL variation of each camera lens can be reduced.